Abstract
BackgroundBursopentin (BP5) is a multifunctional pentapeptide found in the chicken bursa of Fabricius. Recent study indicated that BP5 significantly stimulates expression of p53 protein in colon cancer HCT116 cells. However, the effects and underlying mechanisms of BP5 on HCT116 cell proliferation remain largely unclear.MethodsAnalyses of cell viability, cell cycle arrest as well as apoptosis were performed to study the actions of BP5 on HCT116 cells. Western blot analyse was assayed to measure the cell cycle-related and apoptosis-related proteins. Specific siRNAs targeting IRE1, ATF-6, and PERK were used for IRE1, ATF-6, and PERK knockdown, respectively. Cellular reactive oxygen species (ROS) were detected using a H2DCF-DA green fluorescence probe. Cytosolic free Ca2+ concentrations and mitochondrial membrane potential (ΔΨm) were measured using Fluo-3 AM and JC-1 stains, respectively.ResultsBP5 possessed strong inhibitory effects on the cell growth and induced apoptosis in HCT116 cells. Mechanistically, BP5 arrested the cell cycle at G1 phase by increasing p53 and p21 expression and decreasing cyclin E1-CDK2 complex expression. BP5 treatment dramatically activated the endoplasmic reticulum (ER) stress-mediated apoptotic pathway, as revealed by the significantly enhanced expression of unfolded protein response (UPR) sensors (IRE1α, ATF6, PERK) as well as downstream signaling molecules (XBP-1s, eIF2α, ATF4 and CHOP), and by the significantly altered the BP5-induced phenotypic changes in IRE1, ATF6, and PERK knockdown cells. Additionally, BP5-induced ER stress was accompanied by the accumulation of cytosolic free Ca2+ and intracellular ROS. Furthermore, BP5 treatment resulted in the increase of Bax expression, the decrease of Bcl-2 expression and the reduction of ΔΨm, subsequently causing a release of cytochrome c from the mitochondria into the cytoplasm and finally enhancing the activities of caspase-9 and -3. In addition, z-VAD-fmk, a pan-caspase inhibitor, markedly rescued BP5-induced cell viability reduction and reduced BP5-induced apoptosis.ConclusionsOur present results suggest that BP5 has an anticancer capacity to arrest cell cycle at G1 phase and to trigger ER stress/mitochondria-mediated caspase-dependent apoptosis in HCT116 cells. Therefore, our findings provide insight into further investigations of the anticancer activities of BP5.
Highlights
Bursopentin (BP5) is a multifunctional pentapeptide found in the chicken bursa of Fabricius
Cell viability was investigated after HCT116 cells were incubated with various doses of BP5 (0.5–16 mM) for 24, 48 and 72 h
BP5 arrest cell cycle at the G1 phase We investigated whether BP5 has a potential to arrest cell cycle in HCT116 cells
Summary
Bursopentin (BP5) is a multifunctional pentapeptide found in the chicken bursa of Fabricius. Current chemotherapeutic drugs are effective in the treatment of diseases, but they are related to severe clinical toxicities and the development of drug resistance of cancer cells. For this reason, it is a huge challenge for developing new cytotoxic drugs [2,3,4]. The use of naturally occurring substances have been considered to be an effective and less toxic approach in the treatment of various diseases, including many human cancers [5,6,7]. Several chemotherapeutic drugs developed from natural sources have been studied and are currently being used or are being investigated for cancer treatment
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